Filament Trimming Device Having An Abrasion Resistant Cutting Edge And Method Of Trimming Filaments

ABSTRACT

A filament trimming device for cutting filaments of a toothbrush is disclosed. The filament trimming device includes a cutter and a counter knife, each including at least one cutting edge. The at least one cutting edge of the cutter and the at least one cutting edge of the counter knife are located opposite to each other and the at least one cutting edge of the cutter and the at least one cutting edge of the counter knife each include i) a complementary surface contour, and ii) at least one recess carrying a coating comprising at least a first layer and a second layer.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of European Patent ConventionApplication No. 11007003.4, filed Aug. 27, 2011, the substance of whichis incorporated by reference in its entirety herein.

FIELD OF THE INVENTION

The present disclosure relates to a filament trimming device for cuttingfilaments of a toothbrush. More particularly, the present disclosurerelates to a method of trimming toothbrush filaments.

BACKGROUND OF THE INVENTION

A conventional brush, in particular a toothbrush, comprises a brush headand a shaft or a handle. Individual bristle filaments are groupedtogether to form bristle bundles or bristle tufts which are arranged ina predefined geometry onto the brush head. In some cases, the bristletufts are fastened by anchors or anchor wires into blind ended tuftholes. For fastening, the tufts are looped or bent in a U-shapedconfiguration around such an anchor wire, staple or anchor. Thereby, thefilament ends protrude from the brush head surface in different lengths.Therefore, bristle tufts have to be cut after mounting into thetoothbrush head. Modern toothbrushes often show a curved or unevensurface profile of the brush heads. Complex cuts are often performed bycutting a first group of filaments, bending away the cut filaments,cutting a second group of filaments, bending away the second group andso on. In addition or alternatively, profile cutters can be used whichdirectly cut several groups of filaments into different lengths.Trimming machines used for this purpose are intended to cut a hugeamount of plastic filaments in a continuous high quality. Qualityrequirements increase for more complex surface profiles. Further,quality of the filament cut directly influences the following step ofend rounding of the filaments. The better the filaments are cut, theeasier the filaments are end rounded. Therefore, cutting tools arerequired which precisely cut a huge number of brush head profiles in ahigh quality. There is a further need for methods of filament trimming,wherein the trimmed filament ends show a high quality. Thus, thereexists a need for a profile cutter which is able to cut a huge number offilaments in a high quality. Furthermore, there is a need for methods oftrimming filaments in order to provide high end filament ends.

SUMMARY OF THE INVENTION

Several embodiments are disclosed in the independent claims to exemplifythe subject-matter of the present disclosure. Further embodiments aredisclosed by the subject matter of the dependent claims. In accordancewith at least one aspect, there is provided a filament trimming devicefor cutting filaments of a toothbrush comprising a cutter and a counterknife, each comprising at least one cutting edge. The at least onecutting edge of the cutter and the at least one cutting edge of thecounter knife are located opposite to each other and comprise acomplementary surface contour. Further, the at least one cutting edgesof the cutter and of the counter knife each comprise at least one recesscarrying a coating comprising at least a first layer and a second layer.Said second layer may comprise abrasion resistant particles, such as,for example, carbide particles of at least one element of the fourth,the fifth, the sixth and/or the seventh group of the periodic table.

In accordance with another aspect, there is provided a method fortrimming toothbrush filaments comprising the steps of removing at leastone filament tuft from a plurality of filaments, fixing said at leastone filament tuft in a tuft hole provided by a brush head or a part of abrush head and cutting the free filament ends of the at least onefilament tuft using a cutting device having at least one cutting edgewhich is coated by a first layer and a second layer comprising at leasta carbide of at least one element of the fourth, the fifth, the sixthand/or the seventh group of the periodic table so that carbide-cut freefilament ends are provided.

These and other features, aspects and advantages of specific embodimentswill become evident to those skilled in the art from a reading of thepresent disclosure.

BRIEF DESCRIPTION OF DRAWINGS

The embodiments set forth in the drawings are illustrative in nature andnot intended to limit the invention defined by the claims. The followingdetailed description of the illustrative embodiments can be understoodwhen read in conjunction with the following drawings, where likestructure is indicated with like reference numerals and in which:

FIG. 1A shows a perspective view of an example cutter according toembodiments shown and described herein;

FIG. 1B shows a top view of the cutter shown in FIG. 1A,

FIG. 1C shows a side view of the cutter shown in FIG. 1A;

FIG. 2A shows a perspective view of an example counter knife accordingto embodiments shown and described herein;

FIG. 2B shows a top view of the counter knife shown in FIG. 2A;

FIG. 3A shows a perspective view of a cutting section of a trimmingdevice as according to embodiments shown and described herein;

FIG. 3B shows a magnification of the cutting areas of the cuttingsection shown in FIG. 3A;

FIG. 4 shows schematically the build-up of the coating according toembodiments shown and described herein;

FIG. 5A shows a perspective view of another example cutter according toembodiments as shown and described herein;

FIG. 5B shows a perspective view of another example counter knifeaccording to embodiments as shown and described herein;

FIG. 6A shows a perspective view of another example cutter according toembodiments as shown and described herein;

FIG. 6B shows a perspective view of another example counter knifeaccording to embodiments as shown and described herein;

FIG. 7A shows a perspective view of another example cutter according toembodiments as shown and described herein;

FIG. 7B shows a perspective view of another example counter knifeaccording to embodiments as shown and described herein; and

FIG. 8 shows a brush head of a toothbrush being cut by cutting areas ofa cutting section according to embodiments as shown and describedherein.

DETAILED DESCRIPTION OF THE INVENTION

The following text sets forth a broad description of numerous differentembodiments of the present disclosure. The description is to beconstrued as exemplary only and does not describe every possibleembodiment since describing every possible embodiment would beimpractical, if not impossible. It will be understood that any feature,characteristic, component, composition, ingredient, product, step ormethodology described herein can be deleted, combined with orsubstituted for, in whole or part, any other feature, characteristic,component, composition, ingredient, product, step or methodologydescribed herein. Numerous alternative embodiments could be implemented,using either current technology or technology developed after the filingdate of this patent, which would still fall within the scope of theclaims. All publications and patents cited herein are incorporatedherein by reference.

In accordance with at least one aspect of the disclosure, there isprovided a filament trimming device for cutting filaments of atoothbrush comprising a cutter and a counter knife, each comprising atleast one cutting edge. Said cutting edge may be part of a cutting areaof cutting devices such as cutters, knives, mills, mortisers, trimmers,razor blades, electric shavers etc. The main body of the cutting areamay be manufactured from hot-working tool steel and may be shaped asprotrusions, terraced protrusions, narrowing protrusions or small edges.The cutter and the counter knife may be arranged in the trimming devicesuch that the at least one cutting edge of the cutter and the at leastone cutting edge of the counter knife are located opposite to eachother. In one embodiment, the cutter and the counter knife are arrangedsuch that a gap is provided between the cutting edge of the cutter andthe cutting edge of the counter knife. The gap may be in the range offrom about 0.001 mm to about 0.1 mm, in another embodiment in the rangeof from about 0.003 mm to about 0.05 mm, in yet another embodiment inthe range of from about 0.005 mm to about 0.01 mm, and in anotherembodiment any individual number within the values provided or any rangeincluding or within the values provided.

In addition or alternatively, the cutter and the counter knife maycomprise a complementary surface contour. The cutting edges may compriseany surface contour which can be ground. The limitation for grinding isthe diameter and/or the thickness of the grinding device.

In one embodiment, the minimal corner radius of the curvature of thesurface contour of the cutting edge is less than about 0.5 mm, inanother embodiment less than about 0.3 mm, and in another embodimentless than about 0.15 mm. For example, the surface contour may be acurved shape, a convex shape, a concave shape, a wavelike shape, apolygonal shape, a zigzag shape, a chamfered shape and/or anycombination thereof. In another embodiment, the surface contour is astraight line. Examples for complementary surface contours are cuttershaving a convex surface contour being combined with a counter knifehaving a concave surface contour. Alternatively, two convex surfacecontours having a different radius can be combined as well. As anotherexample, zigzag or wavelike shapes can be shifted to achieve acomplementary profile on the surface of the cutter and the counterknife.

In one embodiment, the trimming device may have a cutter and/or acounter knife, wherein each may have a coated cutting edge. For example,the cutter may be a rotating cutter or guillotine cutter. In addition oralternatively, the counter knife may be a counter cutter working itselfas cutting device and thus having a cutting edge. Alternatively, thecounter knife may be only a counter surface which does not show anycutting activity.

In one embodiment, the cutting edges of the at least one trimming devicecomprise a coating having at least a first layer and a second layer. Allfeatures, whether described in combination or individually, which aredescribed in combination with the coating shall be applicable as well tothe coating of the trimming device. A first material may be deposited tothe surface of the cutting area as a base layer. Suitable materialswhich can be used as the base layer are powder-metallurgical steels. Asuitable method for depositing the first material may be for examplelaser cladding. Then, a second material comprising at least particles ofcarbides of one element of the fourth, the fifth, the sixth and/or theseventh group of the periodic table may be deposited to the first layer.A suitable method for depositing the second material may be for example,laser cladding. Finally, the resulting coating may be sharpened forminga sharp cutting edge. Suitable sharpening machines may be for examplegrinding machines.

In one embodiment, the powder-metallurgical steel may comprise Rockwellhardness (HRc-value) in a range of from about 50 to about 60, in anotherembodiment in a range of from about 55 to about 60, and in anotherembodiment any individual number within the values provided or in anyrange including or within the values provided. In addition oralternatively, the second layer may be selected from the groupconsisting of titanium carbide, niobium carbide, tantalum carbide,chromium carbide, tungsten carbide and mixtures thereof. The examplecarbides may be provided in a matrix material, wherein matrix materialmay comprise nickel, cobalt and/or iron. The carbides may be present inthe matrix material in an amount of from about 60% to about 80%, inanother embodiment in an amount of from about 70% to about 80%, inanother embodiment in an amount of from about 70% to about 75%, and inyet another embodiment any individual number within the values providedor in any range including or within the values provided.

Deposits achieved by laser cladding are metallurgically bound and areperfectly dense, meaning that the coating does not show any porosity.During the laser cladding steps the material of the cutting area as wellas the material used for the first and/or second layer may be molten andthen cooled, thereby forming a layer of heat treatable abrasionresistant steel alloy, which is metallurgically bonded to the body ofthe cutting area. The material of the coating may be added as finepowder. The powder may be deposited via a conveyer to the surface of therecess of the cutting edge directly. The laser beam melts the powder andforms a pool of molten cladding material. The laser and the conveyer aremoved along the recess to be coated. Molten material left behind by themoving laser beam cools down and solidifies again, but now the coatingmaterial is metallurgically bound to the surface of the cutting areaforming an abrasion resistant cutting edge.

In one embodiment, the abrasion resistant coating comprising the firstand second layer may be applied in one or more depositing steps. Thenumber of cladding repetitions depends on the desired thickness of theresulting layer. If the thickness of the layer is small enough to bedeposited once, a single deposition step may be used. If the thicknessof the layer is bigger and may not be applicable in one depositing step,two or more deposition steps may be performed, wherein the material ofeach deposition step is superimposed. In one embodiment, the firstand/or second layers may be deposited twice. Up to three times ofdepositing material to the surface of the cutting area laser claddingcan be performed without intermediate cooling of the body to be coated.Up to three times of depositing material to the surface of the firstlayer laser cladding can be performed without intermediate cooling ofsaid first coating. Generally, the thickness of each sub-layer appliedcan be adjusted by regulating the amount of deposited material and thevelocity of the laser.

According to the disclosed method, a coating should be applied which issufficiently thick to allow resharpening of the cutting edge. Thethicker is the second layer, the more often the abrasion resistantcutting edge can be resharpened. In one embodiment, the thickness of thefirst layer may be in the range of from about 1 mm to about 4 mm, inanother embodiment in the range of from about 1.5 mm to about 3 mm, inanother embodiment in the range of from about 2 mm to about 2.5 mm, andin yet another embodiment any individual number within the valuesprovided or in any range including or within the values provided. Inaddition or alternatively, the thickness of the second layer may be inthe range of from about 0.1 mm to about 2 mm, in another embodiment inthe range of from about 0.5 mm to about 1.5 mm, in another embodiment inthe range of from about 0.8 mm to about 1.2 mm, and in yet anotherembodiment any individual number within the values provided or in anyrange including or within the values provided.

In one embodiment, resharpening of the applied coating may be repeatedat least about 15 times, in another embodiment at least about 20 times,in another embodiment at least about 25 times, and in another embodimentat least about 30 times before a new coating should be deposited ontothe cutting edge. For sharpening and/or resharpening, abrasive wheels orgrinding machines may be used to shape the deposited coating into asharp cutting edge. In one embodiment, the coating cannot be resharpenedinto a sharp cutting edge again. Then, the coating may be removedtotally from the cutting area and a new coating comprising at least twolayers as described above can be applied. Removing of the residualamount of the abrasion resistant coating may be performed using agrinding machine or abrasive wheels.

Generally, laser cladding may be performed using a power laser emittinga monochromatic coherent light beam. In particular, a laser may be usedhaving enough energy to melt the base metal to be coated as well as thecladding material brought in the form of fine powder. Suitable laserswhich can be used are high-power diode lasers, lamp-pumped solid-statelasers, CO₂-lasers or Nd:YAG-lasers. Good results may be achieved, ifthe laser is used out of focus during laser cladding procedure.According to one embodiment, the laser may be used from about 0.5 mm toabout 10 mm out of focus, in another embodiment from about 1 mm to about8 mm out of focus, in another embodiment from about 2 mm to about 5 mmout of focus, and in yet another embodiment out of focus at anyindividual number within the values provided or any range including orwithin the values provided.

During laser cladding the surface of the cutting area may be meltedpartially during deposition of the first layer. Thereby, a metallurgicbond can be achieved between the material of the cutting area and thefirst layer. Thereby, a small transition zone may result comprisingmaterial of the cutting area and the first layer. “Metallurgical bound”means that the coating is fused to the surface of the cutting area insuch that the microstructure at the base of the coating may beintimately linked to the microstructure of the first layer forming atransition zone.

In addition or alternatively, the surface of the first layer may bemelted partially during deposition of the second layer using lasercladding. Thereby, a metallurgic bond can be achieved between thematerial of the first layer and the material of the second layer and asmall transition zone may result comprising material of both layers.“Metallurgical bound” means here that the second layer is fused to thesurface of the first layer in such that the microstructure at the baseof the second layer may be intimately linked to the microstructure ofthe first layer forming a transition zone.

In addition or alternatively, the carbide particles may not be moltenduring laser cladding so that carbide particles as provided may bepresent in the second layer after forming the coating. Alternatively,the carbide particles may be molten during laser cladding. If thecarbide particles melt during laser cladding, the carbide particlessolidify again during cooling forming thin dendrites. Alternatively, thecarbide particles melt partially during laser cladding so that originalparticles and solidified dendrites can be found in the second layer.

Due to the two step procedure a very abrasion resistant coating isachieved. The material for the cutting area of the filament trimmingdevice can be chosen in a cost-saving manner, because no specialrequirements for the body of the cutting area have to be met. Theabrasion resistant properties are provided by the applied coating. Theapplied coating comprises two different layers, namely a base layer anda layer comprising abrasion resistant particles. The first layer whichmay comprise powder-metallurgic steel provides an abrasion resistantcoating itself, but has a lower abrasion resistance than the secondlayer and thus can be used as base layer or bonding layer for the secondlayer. However, elasticity of the coating decreases, when abrasionresistance increases, meaning that a coating which shows a high abrasionresistance may also show the formation of cracks. Said cracks areusually a result of tension due to different material properties of themain body and the coating. By depositing the second layer comprisingcarbide particles on top of the first layer as disclosed herein, thenumber of cracks is reduced. The first layer forms an ideal intermediatelayer having a sufficient abrasion resistance to be a hard basis for thesecond layer and at the same time being elastic enough to avoid theformation of cracks. Thereby, materials having a huge amount of carbideparticles can be used as second layer. Thus, the method disclosedprovides a very abrasion resistant coating which does not show cracks inthe surface during use.

According to another aspect, there is provided a cutting device forcutting animal fibers, such as hairs. In particular, there is provided acutting device for cutting hair of the beard, hair of the head and/orbody hair. In one embodiment, the cutting device may be an electricshaver or a razor. Electric shavers or razors may comprise razor bladescomprising at least one cutting edge which is coated as described above.In one embodiment, the cutting edge of the at least one cutting devicecomprises a coating having at least a first layer and a second layer.The first layer may consist of a powder-metallurgical steel and thesecond layer may comprise at least abrasion resistant particles. Saidabrasion resistant particles may comprise at least carbides of at leastone element of the fourth, the fifth, the sixth and/or the seventh groupof the periodic table. All features, whether described in combination orindividually, which are described in combination with the coating shallbe applicable as well to the coating of the razor or shaver.

According to another aspect, there is provided a method of trimmingfilaments for brushes, for example toothbrushes. The method may compriseproviding a trimming device as disclosed herein and using said trimmingdevice for cutting filaments. A trimming device may be used for trimmingfilaments, comprising all features disclosed herein, whether describedindividually or in combination.

In one embodiment, the method for trimming toothbrush filaments maycomprise the steps of removing and/or picking at least one filament tuftfrom a plurality of filaments. Then said at least one filament tuft isfixed and/or mounted into a tuft hole which is provided by a brush heador a part of a brush head and finally the free filament ends of the atleast one filament tuft are cut using a cutting device as disclosedherein. Said cutting device may comprise at least one cutting edge whichis coated by a first layer which may consist of a powder-metallurgicalsteel and a second layer comprising at least a carbide of at least oneelement of the fourth, the fifth, the sixth and/or the seventh group ofthe periodic table so that carbide-cut free filament ends are provided.“Removing and/or picking” as used herein shall mean any form ofisolating a number of filaments from a bigger number of filaments andtransferring said isolated number of filaments to a separate place.“Fixed and/or mounted” as used herein shall mean that the filament tuftis located in the tuft hole by fixing means. Suitable fixing means maybe for example, clamping means, attaching means or gluing means. “Tufthole” as used herein shall mean any blind hole or through hole of anyform which is located in a brush head, a brush head section, a brushhead carrier or a part thereof. In one embodiment, the filament tuft isstapled using an anchor, in another embodiment the tuft is clamped intoand/or fused to a carrier plate, and/or in another embodiment the tuftis over-molded with plastic material.

In addition, the carbide-cut free filament ends may be end-rounded aftercutting. Carbide-cut filament ends can be end-rounded easier and to ahigher quality, due to the high quality of the cut. Carbide-cutfilaments show very similar cutting lines and less frazzling at the freeends. At least about 1,000,000 brush heads, in another embodiment atleast about 1,500,000 brush heads, and in another embodiment at leastabout 3,000,000 brush heads can be cut as disclosed herein without adecrease in the quality of the cut.

In one embodiment, the final length of at least one filament in thefilament tuft may differ from the final length of at least one otherfilament in the filament tuft after cutting. That means, that a surfacecontour being different from a flat plane can be cut using the cuttingdevice as disclosed herein. In another embodiment, one bristle tuft iscut to one filament length so that a flat plane is achieved. In additionor alternatively, two or more filament tufts may be cut in such that thefinal length of at least one of the two or more filament tufts isdifferent to the final length of the at least other filament tuft. Thatmeans, that a surface contour of a brush head being different from aflat plane can be cut using the cutting device as disclosed herein. Thesurface profile may have a curved shape, a convex shape, a concaveshape, a wavelike shape, a polygonal shape, a zigzag shape, a chamferedshape, or a combination thereof. In another embodiment, all bristletufts of a brush head are cut to one filament length so that a flatplane is achieved. Cutting of a surface profile may be performed in asingle cutting step. If the cutting shall be performed in one cuttingstep, the surface contour of the cutting edge of the cutting devicecorresponds to the surface contour of the brush head after cutting. Twoor more cutting steps can be performed successively with the samesurface profile, thereby increasing the accurateness of the profile cut.Alternatively, cutting of the filaments may be performed in two or morecutting groups. Thereby, a first group of filaments is cut first. Thenthe cut filaments are bent away and a second group of filaments is cutand bent away and so on.

In the following, a detailed description of several example embodimentswill be given. It is noted that all features described in the presentdisclosure, whether they are disclosed in the previous description ofmore general embodiments or in the following description of exampleembodiments, even though they may be described in the context of aparticular embodiment, are of course meant to be disclosed as individualfeatures that can be combined with all other disclosed features as longas this would not contradict the gist and scope of the presentdisclosure. In particular, all features disclosed for either one of thecutter or the counter knife may also be applied to the other one.

FIGS. 1A to 1C show an example embodiment of a cutter 20 according tothe present disclosure. FIG. 1A shows the cutter 20 in a perspectiveview. FIG. 1B shows a top view and FIG. 1C shows a side view of thecutter 20. In this embodiment, the cutter 20 may have an elongatedrectangular main body having a cylindrical hole representing a mountingarea 22. The mounting area 22 may be arranged along a longitudinal axis26 of the cutter 20. The cutter 20 may be attached to a filamenttrimming device 10 by the mounting area 22 in a conventional manner. Forexample, a drive rod can be placed into the mounting area 22 for drivingthe cutter 20 circularly (not shown). At four edges being in parallel tothe longitudinal axis 26 one or more cutting areas 24 may be arranged.The cutter 20 shown in FIG. 1 comprises two cutting areas 24 at each ofthe edges of the main body of the cutter 20 which are located in asingle-plane. The cutting areas 24 may be shaped as terracedprotrusions. The most protruding protrusion may be narrowed to a smalledge representing the cutting edge 12A.

Each cutting edge 12A may be covered by an abrasion resistant coating.To place the coating durably, the most protruding protrusion maycomprise a recess 18. The recess 18A may be shaped to carry the abrasionresistant coating totally to form a sharp cutting edge 12A. Thedimensions of the recess 18A are adapted to completely fit to thedimensions of the coating so that after deposition of the coating asurface is achieved which does not show any rough edges. The cuttingedge 12A may have a surface shape which differs from a straight line.The cutting edge 12A shown in FIG. 1 shows a convex surface contour.

The cutter 20 may be formed by any hard material, for example steel. Dueto the abrasion resistant coating no requirements have to be met by thematerial of the cutter 20. In one example embodiment, the cutter 20 maybe formed from hot-working tool steel or from tool steel, wherein anyhot-working tool steel or any tool steel can be used. In one embodiment,the cutter 20 may consist of X37CrMoV5-1 steel. The abrasion resistantcoating may be applied by laser cladding as described above. In oneembodiment, two layers of different material may be deposited to each ofthe cutting edges 12A of the cutter 20. A first layer 14 may comprisepowder-metallurgical steel. A second layer 16 comprises at leastabrasion resistant particles, for example carbide particles of elementsof the fourth, the fifth, the sixth and/or the seventh group of elementsof the periodic table. A detailed description of the first layer 14 andthe second layer 16 is given in connection with FIG. 4. All featuresdisclosed in FIG. 4, whether described individually or in combinationand which relate to the coating are also applicable to the coating ofthe cutter 20 shown in FIG. 1.

FIGS. 2A and 2B show an example embodiment of a counter knife 30. FIG.2A shows the counter knife 30 in a perspective view and FIG. 2B shows atop view of the counter knife 30. In this embodiment, the counter knife30 may have a rectangular and flat main body. At one of the longer sidesof the rectangular body mounting areas 32 may be arranged suitable tomount the counter knife 30 to a part of a trimming device 10 in aconventional manner (not shown). For example, two or more mounting areas32 may be arranged at one side of the rectangular main body of thecounter knife 30. Opposite to the mounting areas 32, in particular atanother side of the main body of the counter knife 30 one or morecutting areas 34 may be arranged. The counter knife 30 shown as anexample in FIG. 2 comprises two cutting areas 34 which may be shaped aselongated protrusions. The cutting areas are located adjacent to eachother along one side of the counter knife 30. The most protruding end ofthe elongated protrusion may be narrowed to a small edge representingthe cutting edge 12B. The cutting edges 12B are arranged in onesingle-plane.

Each cutting edge 12B is covered by an abrasion resistant coating. Toplace the coating durably, each most protruding part of the cutting area34 comprises a recess 18B which is suitable to carry the coating. Thedimensions of the recess 18B are adapted to completely fit to thedimensions of the coating so that after deposition of the coating asurface is achieved which does not show any rough edges. The cuttingedge 12B may have a surface shape which differs from a straight line.The cutting edge 12B shown in FIG. 2 comprises a convex surface contour.

The counter knife 30 may be formed by any hard material, for examplesteel. Due to the abrasion resistant coating no requirements have to bemet by the material of the counter knife 30. In one example embodiment,the counter knife 30 may be formed by hot-working tool steel or toolsteel, wherein every hot-working tool steel or tool steel can be used.In one embodiment, the counter knife 30 may consist of X37CrMoV5-1steel. The abrasion resistant coating is applied by laser cladding asdescribed above. In one embodiment, two layers of different material maybe deposited to each of the cutting edges 12B of the counter knife 30. Afirst layer 14 may comprise powder-metallurgical steel. A second layer16 comprises at least abrasion resistant particles, for example carbideparticles of elements of the fourth, the fifth, the sixth and/or theseventh group of elements of the periodic table. A detailed descriptionof the first layer 14 and the second layer 16 is given in connectionwith FIG. 4. All features disclosed in FIG. 4, whether describedindividually or in combination and which relate to the coating, are alsoapplicable to the coating of the counter knife 30 shown in FIG. 2.

In FIG. 3, a cutter 20 and a counter knife 30 are shown in workingposition as an example embodiment. FIG. 3A shows a rotating cutter 20and the counter knife 30 as a whole. FIG. 3B shows a magnification ofthe cutting areas 24, 34. The cutting edge 12A of the cutter 20comprises a convex surface contour and the cutting edge 12B of thecounter knife 30 comprises a convex surface contour which iscomplementary to the surface contour of the cutting edge 12A of thecutter 20 regarding size and shape. All features of the cutter 20 andthe counter knife 30 disclosed in the embodiments shown in FIGS. 1 and2, whether described individually or in combination, are also applicableto the embodiment shown in FIG. 3. The same reference signs are used forthe same features as used before in FIGS. 1 and 2.

The cutting area 24 of the cutter 20 and the cutting area 34 of thecounter knife 30 may be arranged opposite to each other in such that thecutting edges 12A, 12B nearly contact each other in the workingposition. “Nearly contact” as used herein shall mean that a small gap 40may be arranged between the cutting edge 12A of the cutter 20 and thecutting edge 12B of the counter knife 30. The size of the gap may be inthe range of from about 0.001 mm to about 0.1 mm, in another embodimentin the range of from about 0.003 mm to about 0.05 mm, and in anotherembodiment in the range of from about 0.005 mm to about 0.01 mm. Usingthe mounting area 22 the cutter 20 may be connected to a drive roddriving the cutter 20 circularly. Drive rod and further parts of thetrimming device 10 are not shown. The counter knife 30 may be connectedto another part of the trimming device 10 via the mounting areas 32.Mounting to the trimming device 10 may be performed in such thatposition and movement of the cutter 20 and the counter knife 30 can beadjusted individually.

A rotating cutter 20 having more than one cutting area 24 may beadvantageous in order to achieve a high efficacy of the trimming device10. The cutter 20 shown in FIG. 3 as an example comprises four pairs ofcutting areas 24 which may be arranged equally over the outline of thecutter 20. In the embodiment shown, four pairs of cutting areas 24 arearranged along the edges of the cutter 20. The pairs of cutting areas 24may be arranged in such that two cutting areas 24 nearly contact twocutting areas 34 of the counter knife 30 simultaneously during rotationof the cutter 20.

FIG. 3B shows a magnification of the cutting areas 24, 34. The coatingis shown at one of the two cutting edges 12A of the cutter 20. At theother cutting area 24 the recess 18A is visualized. At the cutting area34 of the counter knife 30 one recess 18B and one cutting edge 12Bhaving the abrasion resistant coating are shown. In an exampleembodiment of the disclosure, both cutting edges 12A, 12B may be coated.

FIG. 4 shows a build-up of the coating which is deposited to therecesses 18A, 18B of the cutting edges 12A, 12B schematically. Thefeatures disclosed herein regarding the coating are disclosed generallyand are applicable to all embodiments shown. The coating comprises atleast a first layer 14 and a second layer 16. Both layers 14, 16 aredeposited successively onto recesses 18A, 18B provided in a cutting area24, 34 of a cutter 20 or a counter knife 30 using laser cladding. Inaddition, the first layer 14 and/or the second layer 16 may be appliedin one or more depositing steps depending on the desired thickness ofthe resulting layer. In one embodiment, the first layer 14 may comprisea thickness in the range of from about 1 mm to about 4 mm, in anotherembodiment in the range of from about 1.5 mm to about 3 mm, in anotherembodiment in the range of from about 2 mm to about 2.5 mm, and in yetanother embodiment any individual number within the values provided orin any range including or within the values provided. In addition oralternatively, the second layer 16 may comprise a thickness in the rangeof from about 0.1 mm to about 2 mm, in another embodiment in the rangeof from about 0.5 mm to about 1.5 mm, in another embodiment in the rangeof from about 0.8 mm to about 1.2 mm, and in yet another embodiment anyindividual number within the values provided or in any range includingor within the values provided. A thickness in the given ranges can beapplied in one deposition step. Thereby, the thickness of the layer canbe adjusted by regulating the amount of deposited material and thevelocity of the laser. Generally, a coating should be applied which issufficiently thick to allow resharpening of the cutting edge 12A, 12B.The thicker the second layer 16, the more often the abrasion resistantcutting edge 12A, 12B can be resharpened. In one embodiment, the secondlayer 16 is thicker than the first layer 14. In addition oralternatively, the second layer 16 may be applied in more than onedeposition steps.

In one example embodiment, the cutting edge 12A, 12B may be formed by ahot-working tool steel or a tool steel, wherein every hot-working toolsteel or tool steel can be used. In another embodiment, the cutting edge12A, 12B may be manufactured from X37CrMoV5-1 steel.

In addition or alternatively, the first layer 14 may comprisepowder-metallurgical steel. The powder metallurgical steel optionallymay comprise a Rockwell hardness (HRc-value) in a range of from about 50to about 60, in another embodiment in a range of from about 55 to about60, and in yet another embodiment any individual number within thevalues provided or in any range including or within the values provided.Powder-metallurgical steels which may be used are for instance CPMsteels available for example, from Crucible Industries LLC, 440C-steel,Vanadis23-steel, D2-steel, H19-steel, S7-steel, A2-steel, 1.4125-steel,1.2379-steel or 1.2767-steel. Suitable CPM-steels are for example, CPM590V, CPM 9V or CPM 1V. In one embodiment, the powder-metallurgicalsteels may be deposited as a powder comprising particles of severalshapes and/or sizes.

In addition or alternatively, the second layer 16 comprises abrasionresistant particles for example carbides of at least one element of thefourth, the fifth, the sixth and/or the seventh group of the periodictable. Suitable carbides from the fourth group may be titanium carbide,zirconium carbide, hafnium carbide or a mixture thereof. Suitablecarbides from the fifth group may be vanadium carbide, niobium carbide,tantalum carbide or a mixture thereof. Suitable carbides from the sixthgroup may be chromium carbide, molybdenum carbide, tungsten carbide or amixture thereof. Suitable carbides from the seventh group may bemanganese carbide, rhenium carbide or a mixture thereof. Carbides ofseveral groups can be used individually or as a mixture. In oneembodiment, titanium carbide, niobium carbide, tantalum carbide,chromium carbide, tungsten carbide or a mixture thereof is used. Thecarbides may be deposited as a powder comprising particles of severalsizes and/or shapes.

In addition, the carbides may be applied in a matrix. Suitable matrixcomponents comprise other metals, such as elements of the eighth, theninth, the tenth or the eleventh group of the periodic table. In oneembodiment, iron, cobalt, nickel, copper or a mixture thereof may beused as matrix components. The matrix components may be mixed with thecarbides before applying both components as second layer 16 to the firstlayer 14. In one embodiment, the second layer 16 may comprise carbidesin the matrix components in an amount of from about 60% to about 80%, inanother embodiment in an amount of from about 70% to about 80%, inanother embodiment in an amount of from about 70% to about 75% and inyet another embodiment in an amount of any individual number within thevalues provided or in any range including or within the values provided.

In one embodiment, the surface of the recess 18A, 18B provided at thecutting edge 12A, 12B of the cutting areas 24, 34 may be moltenpartially during deposition of the first layer 14 using laser cladding.Thereby, a metallurgic bond can be achieved between the material of thecutting area 24, 34 and the first layer 14 and a small transition zoneresults comprising material of the cutting area 24, 34 and the firstlayer 14. The transition zone is small enough that the first layer 14consisting of the powder-metallurgical steels remains. In addition oralternatively, the surface of the first layer 14 may be molten partiallyduring deposition of the second layer 16 to the first layer 14 usinglaser cladding. Thereby, a metallurgic bond can be achieved betweenmaterial of the first layer 14 and material of the second layer 16, anda small transition zone results comprising material of the first layer14 and of the second layer 16. The transition zone is small enough thatthe first layer 14 which may consist of powder-metallurgical steels andthe second layer 16 comprising carbide particles in a metal matrixremain distinguishable in the applied coating.

FIG. 5A shows a perspective view of another example cutter 20. The samereference signs are used for the same features as used before in FIGS. 1to 4. A rotating cutter 20 is shown having eight cutting areas 24 whichare arranged in pairs along the surface of the cutter 20. Each cuttingarea 24 comprises a cutting edge 12A having a buckled concave surfacecontour. An abrasion resistant coating may be applied to the cuttingedge 12A. The coating may comprise two layers of different materials. Afirst layer 14 may comprise, for instance, powder-metallurgical steeland a second layer 16 may comprise at least abrasion resistantparticles, for example, carbide particles of elements of the fourth, thefifth, the sixth and/or the seventh group of elements of the periodictable. A detailed description of the first layer 14 and the second layer16 is given in connection with FIG. 4. All features disclosed in FIG. 4,whether described individually or in combination and which relate to thecoating, are also applicable to the coating of the cutter 20 shown inFIG. 5A.

FIG. 5B shows a perspective view of another example counter knife 30.The same reference signs are used for the same features as used beforein FIGS. 1 to 4. A counter knife 30 is shown having two cutting areas 34which are arranged as pairs along one side of the counter knife 30. Eachcutting area 34 comprises a cutting edge 12B having a buckled convexsurface contour. An abrasion resistant coating may be applied to thecutting edge 12B. The coating may comprise two layers of differentmaterials. For example, a first layer 14 may comprisepowder-metallurgical steel and a second layer 16 may comprise at leastabrasion resistant particles, for example, carbide particles of elementsof the fourth, the fifth, the sixth and/or the seventh group of elementsof the periodic table. A detailed description of the first layer 14 andthe second layer 16 is given in connection with FIG. 4. All featuresdisclosed in FIG. 4, whether described individually or in combinationand which relate to the coating, are also applicable to the coating ofthe counter knife 30 shown in FIG. 5B. All features of the cutters 20and the counter knives 30 which are disclosed in the embodiments shownin FIGS. 1 to 3 are also applicable to the embodiment shown in FIGS. 5Aand 5B, independent of being described individually or in combination.

FIG. 6A shows a perspective view of another example cutter 20. The samereference signs are used for the same features as used before in FIGS. 1to 5. A rotating cutter 20 is shown having four cutting areas 24 whichare arranged around the outline of the cutter 20. The cutting areas 24are arranged in the middle of the cutter 20. Each cutting area 24comprises a cutting edge 12A having a buckled concave surface contour.An abrasion resistant coating may be applied to the cutting edge 12A.The coating may comprise two layers of different materials. For example,a first layer 14 may comprise powder-metallurgical steel and a secondlayer 16 may comprise at least abrasion resistant particles, for examplecarbide particles of elements of the fourth, the fifth, the sixth and/orthe seventh group of elements of the periodic table. A detaileddescription of the first layer 14 and the second layer 16 is given inconnection with FIG. 4. All features disclosed in FIG. 4, whetherdescribed individually or in combination and which relate to thecoating, are also applicable to the coating of the cutter 20 shown inFIG. 6A.

FIG. 6B shows a perspective view of another example counter knife 30.The same reference signs are used for the same features as used beforein FIGS. 1 to 5. A counter knife 30 is shown having only one cuttingarea 34 which is arranged in the middle of one edge of the counter knife30. The cutting area 34 comprises a cutting edge 12B having a buckledconvex surface contour. An abrasion resistant coating may be applied tothe cutting edge 12B. The coating may comprise two layers of differentmaterials. For example, a first layer 14 may comprisepowder-metallurgical steel and a second layer 16 may comprise at leastabrasion resistant particles, for example carbide particles of elementsof the fourth, the fifth, the sixth and/or the seventh group of elementsof the periodic table. A detailed description of the first layer 14 andthe second layer 16 is given in connection with FIG. 4. All featuresdisclosed in FIG. 4, whether described individually or in combinationand which relate to the coating, are also applicable to the coating ofthe counter knife 30 shown in FIG. 6B. All features of the cutters 20and the counter knives 30 which are disclosed in the embodiments shownin FIGS. 1 to 3 are also applicable to the embodiment shown in FIGS. 6Aand 6B, independent of being described individually or in combination.

FIG. 7A shows a perspective view of another example cutter 20. The samereference signs are used for the same features as used before in FIGS. 1to 6. A rotating cutter 20 is shown having four cutting areas 24 whichare arranged around the outline of the cutter 20. Further, the cuttingareas 24 are arranged in the middle of the cutter 20. Each cutting area24 comprises a cutting edge 12A having a convex surface contour. Anabrasion resistant coating may be applied to the cutting edge 12A. Thecoating may comprise two layers of different materials: For example, afirst layer 14 which is a base layer and which may comprisepowder-metallurgical steel and a second layer 16 which may comprise atleast abrasion resistant particles, for example, carbide particles ofelements of the fourth, the fifth, the sixth and/or the seventh group ofelements of the periodic table. A detailed description of the firstlayer 14 and the second layer 16 is given in connection with FIG. 4. Allfeatures disclosed in FIG. 4, whether described individually or incombination and which relate to the coating, are also applicable to thecoating of the cutter 20 shown in FIG. 7A.

FIG. 7B shows a perspective view of another example counter knife 30.The same reference signs are used for the same features as used beforein FIGS. 1 to 6. A counter knife 30 is shown having only one cuttingarea 34 which is arranged in the middle of one edge of the counter knife30. The cutting area 34 comprises a cutting edge 12B having a convexsurface contour. An abrasion resistant coating may be applied to thecutting edge 12B. The coating may comprise two layers of differentmaterial: For example a first layer 14 being a base layer and which maycomprise a powder-metallurgical steel and a second layer 16 which maycomprise at least abrasion resistant particles, for example, carbideparticles of elements of the fourth, the fifth, the sixth and/or theseventh group of elements of the periodic table. A detailed descriptionof the first layer 14 and the second layer 16 is given in connectionwith FIG. 4. All features disclosed in FIG. 4, whether describedindividually or in combination and which relate to the coating, are alsoapplicable to the coating of the counter knife 30 shown in FIG. 7B. Allfurther features of the cutters 20 and the counter knives 30 which aredisclosed in the embodiments shown in FIGS. 1 to 3 are also applicableto the embodiment shown in FIGS. 7A and 7B, independent of beingdescribed individually or in combination.

FIG. 8 shows the cutting of bristle filaments 44 of a brush head 42.Said bristle filaments 44 are cut by a cutting device 10 as disclosedherein. Two cutting edges 24, 34 having a complementary surface contourare cutting the filament ends like scissors. The resulting surfacecontour of the brush head 42 corresponds directly to the surface contourof the two cutting edges 24, 34.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”.

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A filament trimming device for cutting filaments of a toothbrushcomprising: a cutter and a counter knife, each including at least onecutting edge, wherein the at least one cutting edge of the cutter andthe at least one cutting edge of the counter knife are located oppositeto each other, and wherein the at least one cutting edge of the cutterand the at least one cutting edge of the counter knife each include i) acomplementary surface contour, and ii) at least one recess carrying acoating comprising at least a first layer and a second layer.
 2. Thefilament trimming device according to claim 1, wherein the surfacecontour of the cutting edge of the cutter and/or the surface contour ofthe cutting edge of the counter knife has a curved shape, a convexshape, a concave shape, a wavelike shape, a polygonal shape, a zigzagshape, a chamfered shape, and/or is a straight line.
 3. The filamenttrimming device according to claim 1, wherein the minimal corner radiusof the curvature of the surface contour of the cutting edges is lessthan about 0.5 mm.
 4. The filament trimming device according to claim 1,wherein a gap is located between the at least one cutting edge of thecutter and the at least one cutting edge of the counter knife.
 5. Thefilament trimming device according to claim 1, wherein the gap is in therange of from about 0.001 mm to about 0.1 mm.
 6. The filament trimmingdevice according to claim 1, wherein the cutter is a rotating cutter ora guillotine cutter.
 7. The filament trimming device according to claim1, wherein the first layer comprises a powder-metallurgical steel andthe second layer comprises at least a carbide of at least one element ofthe fourth, the fifth, the sixth and/or the seventh group of theperiodic table.
 8. The filament trimming device according to claim 7,wherein the second layer comprises titanium carbide, niobium carbide,tantalum carbide, chromium carbide, tungsten carbide or a mixturethereof.
 9. A method for trimming toothbrush filaments comprising: a)removing at least one filament tuft from a plurality of filaments; b)fixing the at least one filament tuft in a tuft hole provided by a brushhead or a part of a brush head; and c) cutting the free filament ends ofthe at least one filament tuft using a cutting device having at leastone cutting edge which is coated by a first layer and a second layercomprising at least a carbide of at least one element of the fourth, thefifth, the sixth and/or the seventh group of the periodic table so thatcarbide-cut free filament ends are provided.
 10. The method according toclaim 9, wherein the carbide-cut free filament ends are end-roundedafter cutting.
 11. The method according to claim 9, wherein the fixingof the at least one filament tuft is performed by stapling with ananchor, clamping in and/or fusing to a bristle carrier and/orover-molding with plastic material.
 12. The method according to claim 9,wherein the final length of at least one filament in the filament tuftdiffers from the final length of at least one other filament in thefilament tuft.
 13. The method according to claim 9, wherein two or morefilament tufts are cut and wherein the final length of at least one ofthe two or more filament tufts is different to the final length of atleast one other filament tuft.
 14. The method according to claim 13,wherein the surface profile of the two or more filament tufts has acurved shape, a convex shape, a concave shape, a wavelike shape, astraight shape, a polygonal shape, a zigzag shape, a chamfered shape, ora combination thereof.
 15. The method according to the claim 14, whereinthe surface profile is cut in a single cutting step.